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Forest Health Protection-Asian Longhorned Beetle:
The First Line of Defense

Asian Longhorned Beetle: The First Line of Defense

  • You may not know it, but you are part of the main line of defense against a serious threat to one of our country's most valuable resources… our hardwood trees.
  • Many of our nation's most common hardwoods and shade trees are threatened by a pest against which they have no natural defense, a pest that could change forever the quality of life in our country. That pest is the Asian longhorned beetle, or "ALB" for short.
  • The purpose of this program is to show you how to recognize the Asian longhorned beetle, identify signs of attack, and report suspicious finds. If we are to have any chance of stopping the ALB, people like you will have to help us discover new infestations so they can be contained and destroyed.
  • The Asian longhorned beetle is a native of China and other areas of eastern Asia. In China it causes widespread damage and death in hybrid poplar plantations. These plantations are salvaged and the low-quality, infested wood is sometimes used to make crates and pallets.
  • The beetles are transported to this continent in these infested, wooden packing materials. Once here, they can escape and infest trees in surrounding areas.
  • Prior to 1996, there were no known infestations of ALB in North America. The first infestation in the U.S. was discovered in New York City in 1996. This was followed by the report of a second infestation in Chicago in 1998. Within months of the initial discoveries, Asian longhorned beetles were found in several different urban and suburban settings in both cities. Millions of dollars have been spent trying to rid these areas of ALB and thousands of high-value shade trees already have been lost. ALB also has been found in dozens of port and warehouse locations nationwide. Such accidental introductions have the potential to develop into new infestations of trees.
  • The ALB's favorite host trees are maples, but it will also attack elm, horsechestnut, willows, and poplars. The ALB does not attack conifers or evergreens. Adult females chew out small pits in the bark and lay their eggs in them. The eggs hatch and the young grubs tunnel into the cambium, causing branch die-back. The grubs tunnel deeper into the tree as they grow. This tunneling eventually kills the tree by cutting off the flow of water and nutrients. Tree death is caused by repeated attacks over several years.
  • Because the Asian longhorned beetle spends so much of its life cycle deep inside the tree, traditional insect control methods like insecticides are proving extremely difficult to develop.At this time, removing the infested trees and then burning or chipping them is the only viable option for eradication of the ALB. This is a costly, time-consuming solution which may have severe economic and aesthetic consequences.
  • There are three basic steps to the ALB eradication strategy: eradicate (or destroy) the known infestations; break the pathway of infested wood; and find any undetected infestations.
  • Known infestations are being intensively surveyed and eradicated.Surveying is done with tree climbers, people in bucket trucks, and ground crews with binoculars. Once the infested trees are removed, Federal, state, and local agencies are cooperating to help the affected areas recover. Quarantines in the known infestations place restrictions on the movement of certain types of wood from these areas to prevent ALB from being moved accidentally to uninfested areas.
  • The USDA has taken steps to help fight ALB by breaking the pathway of infested wood from China. Since 1998, all solid-wood packing material from China must be treated before entering the United States.
  • Perhaps the most important part of ALB eradication is the early detection of infestations. This is where your assistance is so vital.Why do we need your help? There are so many places that the ALB may be present, and looking for attacked trees is so difficult and time-consuming that the regulatory agencies cannot do the job alone.If we can inform citizens, especially people who work regularly with trees, we can greatly improve our odds of finding infestations quickly enough to eradicate them. Finding new infestations as soon as possible may make the difference between getting rid of ALB completely and having to live with this serious tree pest on a permanent basis.
  • In order for you to help with early detection of ALB infestations, it is necessary to know a little bit about the beetle.
  • Like many insects, the beetle has 4 life stages: egg, grub, pupa, and adult. The most destructive life stage is the grub, but these are not likely to be seen because they burrow into the tree.
  • The best way to spot an infestation is by observing the actual adult beetle. The adult beetles are large: ¾ to 1 ¼ inches long.* They are jet-black with distinctive white spots on the back.
  • They have antennae which are black-and-white banded and very long: 1½ to 2 times longer than the beetle's body.In addition, the feet and legs often have a bluish tinge.
  • The most common time of the year to spot the adult beetles is June through October.
  • There are a few native beetles that resemble the Asian longhorned beetle. Beetles such as the white-spotted pine sawyer and the cottonwood borer may be easily confused with ALB. Although they have some charactersitics that are different from ALB, many people may not be able to tell them apart with certainty. It is better to be safe than sorry - if you see any beetle that may be an Asian longhorned beetle, be sure to follow the steps we will give you shortly to report your find.
  • Even if you don't observe the actual adult ALB, there are signs of damage that can warn you that an ALB infestation may be taking place. The most definitive sign of damage is the distinct exit hole. After pupating, the mature adult chews its way out of the tree to disperse and mate. This leaves a perfectly-round exit hole on the outside of the tree. This hole is 3/8 to ½ inch in diameter** and looks as clean as a hole made with a drill.
  • There are other, less-definitive signs that an ALB infestation may be happening. Egg sites are oval to round pits in the tree bark chewed out by the adult female for egg placement. Often, sap is seen flowing from these egg sites.
  • As the ALB grubs bore into a tree, they create sawdust that is pushed out of their tunnels. This coarse sawdust often builds up where branches come together, where branches meet the main stem, and around the bases of the attacked trees. Sap or sawdust alone are not signs that a tree is infested with ALB, as other insects or activities may cause these signs to occur. However, if you see sap or sawdust on a maple tree or one of the other major host trees, these may be warning signs that ALB is present and you should look carefully at the rest of the tree for beetles, exit holes, or egg sites.
  • As important as knowing what to look for is where to look. Maples are ALB's favorite host trees. If you have maples in your area, this is the most likely place for an infestation to start. Accordingly, you should be most alert for ALB in and around maple trees.
  • Other trees that attract the ALB are elm, horsechestnut, willows, and poplars. ALB will attack additional tree species as well, although not commonly. A complete list of host trees in North America has yet to be established. Look for ALB on live and dying hardwood trees, but not on completely dead trees because ALB does not attack these.
  • One reason that infested trees are difficult to spot is because the ALB usually attacks smaller branches in the tree crown first. Only later, when the beetles are attacking the larger branches and main stem, can signs of attack be seen from ground level. The most thorough way of inspecting a tree is to look at all parts of it (with the exception of the branch tips).
  • What should you do if you see a possible ALB infestation? If you see a beetle that might be an ALB, try to capture it in a container and place the container in the freezer to kill and preserve the specimen. Be sure to write down exactly where and when you found the beetle. Noting the exact location is critical so follow-up surveys can be done. In some cases it may be necessary to mark the tree in question with paint or flagging.
  • If you see exit holes, egg sites, or sawdust which may have been made by ALB, once again write down detailed location information for the tree and also note the specific location in the tree where you saw the hole.
  • Any information you have on possible ALB attacks should be passed on to your supervisor, company owner, or one of the following agencies.
    • County cooperative extension, state department of agriculture, state forestry department or state department of natural resources, USDA Animal and Plant Health Inspection Service, or USDA Forest Service.A list of specific contact phone numbers for your area has been provided along with this video.
  • You are truly one of the first lines of defense against this serious pest. With every passing day that an Asian longhorned beetle infestation goes undetected, our chances of eradicating it from the U.S. decrease. You might ask, "exactly what is at risk from the Asian longhorned beetle if we don't eradicate it?" Roughly 30% of urban and suburban trees in the U.S. are maples, ALB's main target. The various forest-related industries at direct or indirect risk from ALB are valued at $41 billion. In the eastern U.S. alone, 4 million jobs depend on forests that the Asian longhorned beetle may damage. Finally, there are immeasurable aesthetic and sentimental values associated with many trees the ALB may kill. You can see that the ALB could become a serious problem nationwide if we are not alert. Please make it a habit to look for and notice the things we've discussed.
    • The presence of the large, striking adult beetle with its white-spotted body and long, banded antennae.
    • The perfectly-round and smooth exit holes on the outside of trees. The exit holes are 3/8 to ½ inch in diameter**.
  • The ALB is a serious pest, but with your help on the main line of defense, we can stop it before irreparable harm is done to our nation's valuable hardwood and shade trees.
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Page Contact: Keith Tackett
June 28, 2011